Yarn trappers for use with lower yarn detector switches have been known heretofore. For example, E. G. Haderer et al. U.S. Pat. No. 4,027,121, dated May 31, 1977, owned by the assignee of this invention, shows a yarn trapper for a yarn detector switch having a two-turn wire helix with the ends of the wire bent to diverge laterally to form a V-shaped guide for the yarn and then bent parallel to one another and the extreme tips being bent toward one another for snap-on mounting on the yarn detector switch.
While such prior known yarn trapper has been useful for its intended purpose, it has not performed 100 percent of the time because the yarn must enter between a full turn and a half turn. That is, this two-turn helix has a full turn at the center and a half turn at each end with the half turns being above and below, respectively, of the level of the supporting arms to form two arcuate slots, one of which will not receive the yarn as fully as the other thereby to cause occasionally failure to trap the yarn.
W. R. Keen U.S. Pat. No. 2,706,883, dated Apr. 26, 1955, shows a thread trapping means having an arm adjustably mounted on a horizontal rod by a set screw. Rigidly secured to this arm is a wing-like component having a horizontal elongated slot. Pivoted on such arm is a thread-contacting trip finger that is counterweighted to swing this finger when the thread breaks. On the counterweight is a lateral projection. With its ends anchored in such lateral projection on the counterweight is a downwardlybowed closely-wound elongate coil segment which may be of spring wire or other suitable stiff strand material, and which is capable of entering with clearance all around it, into the straight elongate slot of the laterally-projecting portion of the fixed wing-like component. Since the thread normally extends between the coil and the slot, tripping the finger will allow the counterweight to fall and cause the coil to press the thread across the slot to trap it between the turns of the coil.
While the latter thread trapper appears to be useful for its intended purpose, it nevertheless is rather complex in structure and non-economical and difficult to manufacture and assemble.
This invention relates to improvements thereover.